View Single Post
Old 22-Jan-2021, 2:27 PM   #7
Junior Member
Join Date: Feb 2013
Location: Western NY State
Posts: 27
Back to plan A, it's a 'no go', it's not the 'silver bullet'

What looked good on paper, wasn't in the field. After experimenting with this on my bench, not where the device would be placed, I finally did install it in place. Results overall were about the same except for a few 'variables' due to the additional 25 or so feet of additional cable between inside locations.

Splitting that one antenna feed via a 16db 'tap' to limit loss of the 'wanted' stations, then reduce the overload of the unwanted 'problem' stations using the 'Tap' out, apparently just added more complexity.
It made the one wanted station somewhat worse. So I went back to just using 2 inputs, but that just got me to where I was before this entered the picture.
This gross signal difference (around 40db between adjacent channels off the antenna) is way too great for this to handle, even with the 20db reduction of that after my traps. Compounding that is the 'slop' left over of the offending adjacent channel from their filters too narrow filter 'shape factor'. (There is a 'wide' and 'narrow' shape factor that is based on if there are adjacent channels active or not)

The Avant-X filters have a tighter 'Q' factor then my custom 'PAR' 'traps' I have (which is good), BUT, the incorrect width doesn't get rid of enough of the adjacent 'haystack', or lets too much empty spectrum in.

Now, having said that, there is a fine line (almost literally) between just how tight a filter/trap is. Frequency and cost come into play. The 'math' is above my pay grade, but since I have 20+ years of tuning traps (as I call them), it's not just a 'art', but a major math problem in design. It's a classic case of "Robbing Peter to pay Paul" between attenuating an adjacent channel while trying to persevere the wanted channel. It really can't be done fully, it's all compromises.

I have proved it more than once, without my custom traps, this would of been completely un-usable, as I stated earlier mostly due to excessive gain and filter width. I LOOSE channels including one VHF (which I can only guess it's because of noise, but that is just an educated guess), not because of any adjacent channels or excessive signal strength. That alone is a deal killing as those custom traps were almost the cost of this.

When I went back to my existing setup (the Winegard DA), two of the stations that were missing, locked back in. That was enough and the two months of fighting with this to get it to work. It was returned. I just couldn't justify the cost in spite of the time I put into this.

Below are pics of the testing, then the final setup in the attic, (not a crawl space) and a scan of the 'traps' that allow to Winegard DA-1018 DA to work where the Avant-X didn't. (The double trace was the traps flipping the order to see if that mattered, the 'dips' are ch 15 & 16 then 31 & 32)
Attached Images
File Type: jpg Anant-X Head End small.JPG (273.4 KB, 380 views)
File Type: jpg Winegard MATV Head End 02-21 small.JPG (270.0 KB, 328 views)
File Type: png Can 16-32 & 32-16 traces.png (16.1 KB, 333 views)

Last edited by videobruce; 8-Mar-2021 at 2:30 PM. Reason: final conclusions & determinations
videobruce is offline   Reply With Quote